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Biomedical subjects

D Osborn

Publications and source records attributed to D Osborn.

At least 37 records · Page 2Linked to original sources
PubMed2000

Intraocular involvement in multifocal fibrosclerosis.

OBJECTIVE: To report the clinical and histopathologic findings of intraocular involvement in a patient with multifocal fibrosclerosis and the response of the patient's choroidal masses to external beam radiotherapy. DESIGN: Case report with clinicopathologic correlation of enucleated eyes. METHODS: The patient was studied by clinical observation, contact B- and A-scan ultrasonography, orbital magnetic resonance imaging, fluorescein angiography, indocyanine green angiography, choroidal biopsy, and gross and histopathologic examination of the enucleated eyes. Tissue obtained at an earlier laparotomy was also reviewed. External beam radiotherapy was used when high-dose corticosteroid and low-dose methotrexate therapy failed to decrease the size of the choroidal masses or improve the patient's vision. MAIN OUTCOME MEASURES: Changes in the clinical and ultrasonographic size of the choroidal masses, the clinical appearance of these masses, and the patient's visual acuity in response to external beam radiotherapy were monitored premortem. Histopathologic findings in the enucleated eyes were compared with the changes in previous abdominal and choroidal biopsy specimens and with tissue alterations reported in multifocal fibrosclerosis. RESULTS: Biopsy of the choroidal mass revealed a fibrosclerosing process similar to that found in the abdomen. The patient received external beam radiotherapy with disappearance of the masses. Fibrosclerosing changes similar to those seen in the abdomen were observed replacing the choroid in the enucleated eyes. CONCLUSIONS: Multifocal fibrosclerosis may involve the choroid with histopathologic changes similar to those that have been described in other locations in the body. External beam radiotherapy may be an effective treatment for intraocular involvement by multifocal fibrosclerosis.

Aged↗
PubMed1999

Quantitative structure-toxicity relationships for halogenated substituted-benzenes to Vibrio fischeri, using atom-based semi-empirical molecular-orbital descriptors.

Quantitative structure-toxicity relationships (QSTR's) are derived for an extensive series of halogenated benzenes, anilines, phenols, nitrobenzenes, toluenes and other substituted benzenes against Vibrio fischeri using a wide range of whole molecule and atom-based descriptors derived from semi-empirical molecular-orbital calculations. In terms of direct statistical correlation with toxicity it was found that the molar refractivity was the most important parameter, closely followed by the solvent accessible surface area of the compound. The accuracy of these descriptors in fitting the numerous fluoro- and chloro-mono-aromatic compounds was compared with bromine and iodine analogues, where the 'best' descriptors for the former were found in general to be less accurate for the latter in the case of multi-halogen substitution. The equations obtained were also used to classify the compounds into narcosis-based mechanisms of toxicity and those with respiratory uncoupling potential. A combination of the molar refractivity and the nucleophilic susceptibility of one of the meta ring carbons predicted the toxicity of the halo-benzenes and toluenes, along with anisoles, benzonitriles, nitrobenzenes and most of the anilines. The relevance of these descriptors to developing coherent and more generally applicable models for QSTR's of mono-aromatic compounds to other species in environmental toxicology is discussed.

Benzene Derivatives↗
PubMed1999

Quantitative structure-toxicity relationships for chlorophenols to bioluminescent lux-marked bacteria using atom-based semi-empirical molecular-orbital descriptors.

Literature data on the toxicity of chlorophenols for three luminescent bacteria (Vibrio fischeri, and the lux-marked Pseudomonas fluorescens 10586s pUCD607 and Burkholderia spp. RASC c2 (Tn4431)) have been analyzed in relation to a set of computed molecular physico-chemical properties. The quantitative structure-toxicity relationships of the compounds in each species showed marked differences when based upon semi-empirical molecular-orbital molecular and atom based properties. For mono-, di- and tri-chlorophenols multiple linear regression analysis of V. fischeri toxicity showed a good correlation with the solvent accessible surface area and the charge on the oxygen atom. This correlation successfully predicted the toxicity of the heavily chlorinated phenols, suggesting in V. fischeri only one overall mechanism is present for all chlorophenols. Good correlations were also found for RASC c2 with molecular properties, such as the surface area and the nucleophilic super-delocalizability of the oxygen. In contrast the best QSTR for P. fluorescens contained the 2nd order connectivity index and ELUMO suggesting a different, more reactive mechanism. Cross-species correlations were examined, and between V. fischeri and RASC c2 the inclusion of the minimum value of the nucleophilic susceptibility on the ring carbons produced good results. Poorer correlations were found with P. fluorescens highlighting the relative similarity of V. fischeri and RASC c2, in contrast to that of P. fluorescens.

Burkholderia↗
PubMed1998

Proton spectroscopy in myotonic dystrophy: correlations with CTG repeats.

OBJECTIVES: To seek cerebral metabolite abnormalities in patients with myotonic dystrophy and to determine whether the degree of cerebral abnormalities (measured by proton magnetic resonance spectroscopy) correlates with severity of the genetic defect (measured by trinucleotide repeats). DESIGN: Fourteen patients with myotonic dystrophy were compared with 24 healthy control subjects. SETTING: A university-affiliated medical center. RESULTS: Compared with healthy subjects, patients with myotonic dystrophy had elevated levels of myoinositol (+19% in the occipital region and +12.9% in the temporoparietal region), total creatine (+7.6% and +6.8%), and choline-containing compounds (+21% and +7.7%). Furthermore, the creatine and myoinositol peak areas correlated with the number of trinucleotide cytosine-thymine-guanine(n) (CTG)n repeats from leukocytes, especially in the temporoparietal brain region (r=0.76; P=.004). CONCLUSIONS: Neurochemical alterations observed with proton magnetic resonance spectroscopy are proportional to the cytosine-thymine-guanine repeat size. Increases in myoinositol and creatine concentrations may be caused by increased glial content, while elevated levels of choline-containing compounds are most likely caused by increased glial content and cell membrane abnormalities. Proton magnetic resonance spectroscopy is a powerful noninvasive tool to study brain biochemistry, which may reflect the extent of neuropathological involvement in patients with myotonic dystrophy.

Adult↗
PubMed1998

Polycyclic aromatic hydrocarbon (PAH) dispersion and deposition to vegetation and soil following a large scale chemical fire.

Polycyclic aromatic hydrocarbons (PAHs) were determined in soil and vegetation following a large scale chemical fire involving 10,000 ton of polypropylene. In comparison with sites outside the plume from the fire, PAH concentrations were elevated in grass shoots (by up to 70-fold) and in soil (by up to 370-fold). The pattern of PAH dispersion under the plume was dependent on the physical-chemical properties of individual PAHs. The lighter, least hydrophobic PAHs were dispersed into the environment at greater distances than heavier, more hydrophobic PAHs. At the most distant sampling point (4.5 km) under the plume, the low molecular weight PAHs were still considerably elevated in vegetation samples compared to control sites. Dispersion appeared to be regulated by the compounds partitioning between the vapour and particulate phase, with dry particulate deposition occurring closer to the fire source than gaseous deposition. For all PAHs, the fire resulted in greater contamination of soils compared to grasses, with the relative ratio of plant/soil contamination decreasing as hydrophobicity increased.

Journal Article↗
PubMed1997

Dioxin and furan residues in wood mice (Apodemus sylvaticus) following a large scale polyvinyl chloride (PVC) fire.

A forest ecosystem was contaminated as a result of a fire involving 600 t of PVC. A wide range of 2,3,7,8-substituted dioxin and furan congeners were elevated (by up to 4-fold) on soil adjacent to the factory compared to a site 200 m from the factory perimeter. Livers of wood mice (Apodemus sylvaticus) caught on these areas were also analysed for dioxins and furans. Toxic equivalents (TEQs) were 9-fold higher in wood mice caught on the site 10 m from the factory perimeter compared with the site 200 m from the perimeter, with individual 2,3,7,8-substituted congeners being elevated by up to 30-fold. Wood mouse liver TEQs were found to be highly correlated with cadmium kidney concentrations, cadmium also being found at elevated concentrations at the accident site. There was also a significant positive correlation between wood mouse liver TEQs and relative liver weights (wet weights expressed as a percentage of total body weight). The results of this study are discussed in the wider context of dioxin contamination in the environment.

Journal Article↗
PubMed1993

Effect of bovine serum albumin on passive transfer of immunoglobulin G1 to newborn calves.

The molecular mechanism in the intestine of newborn calves that results in transfer of intact colostral immunoglobulin from the lumen to the circulation also is capable of transferring a variety of non-immunoglobulin macromolecules. If the capacity of this mechanism is limited, transfer of a large amount of non-immunoglobulin protein may interfere with transfer of immunoglobulin. In this experiment, efficiency of IgG1 transfer in newborn calves was reduced from 59 to 36% by the addition of bovine serum albumin (37 mg ml-1) to colostral whey, while the addition of a similar mass of amino acids in the form of acid hydrolyzed casein (37 mg ml-1) did not detectably alter IgG1 transfer. Reduced IgG1 absorption efficiency in calves fed colostrum with added bovine serum albumin is consistent with a limited capacity for the macromolecular transport mechanism in the intestine of newborn calves.

Animals↗
PubMed1993

Reliability of in vivo volume measures of hippocampus and other brain structures using MRI.

Volume reductions of the hippocampus are associated with Alzheimer's disease, schizophrenia, and epilepsy. We used clinically available MRI methods (2D acquisition; inversion recovery and calculated T2 images; 3 mm contiguous slices) that optimize image contrast, quality, and resolution and standardized positioning protocols to maximize the in vivo accuracy (test-retest reliability) of brain volume measurements in volunteers who were scanned two or three times. Volunteers were scanned in the same MRI instrument (intrascanner reliability) as well as in two different instruments (interscanner reliability). A single rater obtained brain volume measures of seven contiguous slices centered on the anterior commissure. The in vivo intrascanner reliability for measures of anterior hippocampus and ventricular volumes was very good, with reliability coefficients [intraclass r (rxx)] ranging between .855 and .997, and a median coefficient of variation (CV) of 6.4%. Reliability was good for amygdala (rxx of .740 and .764) and for total frontal and temporal lobe volumes and white matter volume measures (rxx ranging between .640 and .823, median coefficient of variation was 3.2%). Overall, interscanner reliability was also good. We discuss the implications of our results relative to the possible clinical utility of hippocampal quantification and the feasibility of prospective studies aimed at quantifying progressive neurodegeneration.

Adult↗
PubMed1988

Polycarbonate intraocular lenses.

Bisphenol-A polycarbonate has been investigated as an improved polymer for ocular implants, especially for intraocular lenses (IOLs). Polycarbonate properties afford special opportunities for development of tougher, stronger, one-piece IOLs. Autoclave or gamma sterilizability and a higher refractive index may provide additional IOL advantages over polymethylmethacrylate. Implant studies in rabbits have shown polycarbonate IOLs to be well tolerated in the anterior chamber for 2.5 years. Polycarbonate appears promising for new IOLs and other ocular implant applications.

Animals↗
PubMed1987

Relationships between tissue contaminant concentrations in a small sample of seabirds.

1. The metal and organochlorine contaminant concentrations were measured in a small sample of three seabird species collected from St Kilda, Scotland, UK, and the relationship between concentrations of different contaminants within and between tissues was compared. 2. There was little evidence that the concentration of a contaminant in one tissue was indicative of the concentration in any other tissue. 3. Generally, different contaminants had not co-accumulated in tissues; this was so even for the lipophilic compounds (DDE and PCBs), with the exception of puffin fat. 4. There was a tendency for the species containing the most fat to contain the highest concentrations of lipophilic contaminants and there was some suggestion that the fat in muscle could play a role in determining PCB concentrations.

Animals↗
PubMed1985

Uterine rupture in Nigeria.

Uterine rupture in the developing world remains a significant problem. We treated 45 such cases. The predisposing factors included cephalopelvic disproportion (62%), grand multiparity (33%), previous cesarean section (24%), placental pathology (15%) and abnormal presentation (20%). The factors associated with maternal death included sepsis (71%), macerated stillborn infant (60%), vulvar edema (50%), hand presentation (50%), prolonged labor (42%) and hysterectomy (37.5%). Hemodynamic resuscitation and prompt surgical intervention remain the mainstays of therapy.

Adolescent↗
PubMed1984

Comparative distributions of zinc, cadmium and mercury in the tissues of experimental mice.

Different groups of mice were injected with cadmium, zinc and mercury. Zinc injections had no effect on zinc tissue levels while both mercury and cadmium accumulated in various tissues. Cadmium persisted in the tissues much longer than mercury, and while the mercury concentrations began to decline as soon as dosing ceased, cadmium concentrations in kidney and intestine increased even after dosing ceased. There appeared to be an interrelationship between cadmium concentrations in spleen and intestine which warrants some further investigations. There was a linear, but discontinuous, effect of cadmium on zinc concentrations in liver, kidney and pancreas which may depend on metallothionein biochemistry. Mercury injections had no effect on zinc metabolism. It is proposed that differences in the rate of excretion of cadmium and mercury from the kidney could explain the differential accumulation of cadmium and mercury in animals.

Animals↗